Individual pairs of telephone circuit wires are frequently terminated in telephone company central offices, distribution cabinets and customer premise locations, for example, utilizing multi-terminal connector blocks. Once terminated, these telephone circuit wires, usually comprised of cables containing narrow gauge insulated copper conductors, are grouped and then rerouted for appropriate distribution of the calls which they carry. Single connector blocks normally accommodate anywhere from 60 to 100 pairs of densely packed terminations, wherein multiple connector blocks are frequently contained in close proximity at a single location, e.g., one wall of a telephone switching room. Efficient utilization of mounting space is thus required since space within utility locations is traditionally at a premium.
Besides the incoming circuit terminations, the connector blocks are also utilized for making cross-connections from individual circuits on the connector blocks, as well as for the mounting of current and voltage limiting circuit protection used to prevent damage caused by lightening and other external forces. As is known, circuit protection devices which provide both current and voltage limiting circuit protection are polarity sensitive with respect to the individual pairs of wires being protected. Thus, when a double sided connecting block is utilized, wherein common pairs of terminals are included on both the front and rear of the connecting block, circuit protection devices adapted for installation on the front side of the connecting block are generally not compatible to provide circuit protection on the rear of the connecting block because the polarity will be reversed. Erroneous installation of a front circuit protection device in the rear of a connecting block and/or installation of a rear protection device in the front of a connecting block may render the communications circuit inoperable, or at the very least, improperly protected.
It is therefore an object of the present invention to provide a mounting interface for a double sided connecting block which ensures that polarity sensitive circuit protection devices cannot be improperly installed.